RIBs Architecture Questions

Has anyone here used RIBs architecture before? I’m starting a new cross platform mobile project using it. I’m trying to figure out:
For Android whether to use Kotlin or Java,
For iOS whether to use SwiftUI or UIKit
What good dependency injection practices using needle and RIBs are? Does needle replace RxSwift?
How and where to properly use “Plugins” on a more practical level
How to write unit tests for the interactor. Unfortunately I have almost no experience writing unit tests in Java/Kotlin & Swift but I really want to learn.

Thank you for reading this and I greatly appreciate any assistance.